1. Field of the Invention
The present invention relates to a two-step push-on switch in which first and second switches are sequentially turned ON as a result of a depressing operation.
2. Description of the Prior Art
Conventionally, a two-step push-on switch is known in which a movable contact plate that is formed by a metal plate spring, and that has: an annular peripheral plate portion; a center plate portion upward inflatingly curved; and a connecting plate portion connecting these plate portions together is placed in a switch case incorporating first and second stationary contacts, and, as a result of an operation of depressing the center plate portion, the connecting plate portion is downward inclinedly inverted to make contact with the first stationary contact (a first switch is turned ON), and subsequently the center plate portion is inverted to a downward inflated state to make contact with the second stationary contact (a second switch is turned ON) (for example, see Japanese Utility Model Publication No. 7-53234).
A technique for thinning a push-on switch has been proposed in which an adhesive tape is applied directly to the upper face of a movable contact plate configured by a spherical click spring, to fix the plate onto a circuit board such as a printed circuit board (PCB) or a flexible printed circuit board (FPC) where a stationary contact that is to make contact with the movable contact plate is disposed (for example, see Japanese Patent Application Laying-Open No. 2003-77368).
The technical concept disclosed in Japanese Patent Application Laying-Open No. 2003-77368 or the like may be applied to the two-step push-on switch disclosed in Japanese Utility Model Publication No. 7-53234 or the like, to configure a very thin two-step push-on switch. In this case, the adhesive tape sticking to the peripheral plate portion of the movable contact plate deteriorates the operation characteristics (elasticity) of the peripheral plate portion such as expansion and contraction, whereby the first-step pressing load for turning ON the first switch is increased, and the first-step sense produced when the first switch is turned ON is blunted (deteriorated). Therefore, a problem which is to be solved by the invention is that a movable contact plate configured by a metal plate spring cannot be fixed by an adhesive tape onto a circuit board without deteriorating the operation characteristics of the movable contact plate.